Bobbins with open slots for wire leads.
Available sizes:
EI 38 - EI 192 / catalog pages 37-39
UI 30 - UI 180 / catalog pages 103-107
M 30 - M 102 / catalog pages 11
For UI-laminations we can provide bobbins with guide ribs for automatic insertion of laminations, see catalog pages 111 - 112.